This invention relates to a method and system of controlling the effective value of alternating current to a preset value.
In an alternating current system wherein alternating current is supplied to an AC load through a pair of controlled semiconductor switching elements, for example thyristors, which are connected in parallel opposition, it is desirable to maintain the effective value of the alternating current at a prescribed set value and to change the set value when desired. However, as will be described later in more detail according to a prior art method and system where the power factor of the load varies greatly it has been difficult to increase the response speed of the system and to improve the stability thereof.